lib/libc/arch/powerpc64/gen/makecontext.c

   1 /*      $NetBSD: makecontext.c,v 1.3 2008/04/28 20:22:57 martin Exp $   */
   2
   3 /*-
   4  * Copyright (c) 2001 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Klaus Klein.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 __RCSID("$NetBSD: makecontext.c,v 1.3 2008/04/28 20:22:57 martin Exp $");
  35 #endif
  36
  37 #include <inttypes.h>
  38 #include <stddef.h>
  39 #include <ucontext.h>
  40 #include "extern.h"
  41
  42 #if __STDC__
  43 #include <stdarg.h>
  44 #else
  45 #include <varargs.h>
  46 #endif
  47
  48 void
  49 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
  50 {
  51         __greg_t *gr = ucp->uc_mcontext.__gregs;
  52         __greg_t sp, *spp;
  53         int i;
  54         va_list ap;
  55
  56         sp  = (__greg_t) ((uintptr_t)ucp->uc_stack.ss_sp
  57             + ucp->uc_stack.ss_size);
  58         sp -= 2 + (argc > 8 ? argc - 8: 0); /* Make room for call frame. */
  59         sp  = (__greg_t) ((uintptr_t)sp & ~0xf);
  60
  61         /*
  62          * Start executing at <func> -- when <func> completes, return to
  63          * <_resumecontext>.
  64          */
  65         gr[_REG_R1]  = sp;
  66         gr[_REG_LR] = (__greg_t)_resumecontext;
  67         gr[_REG_PC] = (__greg_t)func; // XXX -- this is the descriptor address!
  68
  69         /* Wipe out stack frame backchain pointer. */
  70         spp = (__greg_t *)sp;
  71         *spp = 0;
  72
  73         /* Construct argument list. */
  74         va_start(ap, argc);
  75         /* Up to the first eight arguments are passed in r3-10. */
  76         for (i = 0; i < argc && i < 8; i++)
  77                 gr[_REG_R3 + i] = va_arg(ap, long);
  78         /* Pass remaining arguments on the stack above the backchain/lr gap. */
  79         for (spp += 2; i < argc; i++)
  80                 *spp++ = va_arg(ap, long);
  81         va_end(ap);
  82 }